Airplane landing gear



April 7. 942 1.. c. SjTEARMAN 2,279,074

- AIRPLANE LANDING GEAR Filed June 19, 1939 -FIIE IL INVENTOR l/oya C. 5/ea'rman BY A2 54.4

ATTORNEY Patented-Apr. 7, 1942 UNITED STATES PATENT OFFICE- AIRPLANE LANDING Gran new 0. shame, 'Burlingame, assignmto Transair Corporation, San Francisco, Calif., a corporation of California Application June 19, 1939,- Serial No. 279,908

' This invention relates generally to landing gear for airplanes and is concerned more particularLv with the provision of an improved steering mechanism for a retractable wheel of such landing gear.

. It is a general object of the invention to provide improved steering mechanism for the landing gear of an airplane.

Another object of the invention is to provide an improved steering mechanism of the character referred to which canbe enabled or disabled selectively.

Another object of the invention is to provide improved steering mechanism for a retractable wheel in the landing gear 01 an airplane.

Another object of the invention is to provide improved steerlng'mechanism for the retractable wheel of the landing gear, in which the steering mechanism is automatically disabled when the wheel is retracted.

, Another object of the invention is to provide a landing gear of the character referred to, in which the steerable wheel can be controlled either for steering movement or for free swivel! ling movement.

5 Claims. 101144-50) it is moved from its ground-engaging position to its retracted position. t Y

The. landing wheel l0, Fig. 1, is journalled on axle ll carried by a bracket arm [2 depending from a rod l3 which is connected through suitable shock absorbing means with a cylinder I 4'. Cylinder ll is-joumalled in spaced bearings 16 forming part of the strut construction I! having trunnions l8 journalled in bearings IQ of the airplane structure. .Bearings 16 also prevent endwise movement of tube. The pivotal connection of the strut construction 3 I! with the bearings l9 provides for movement of the wheel I 0 between its, ground-engaging position shown in full lines and its retracted or flying'pbsition shown in dotted lines.

. The rod l3 and the cylinder l4 form part of a conventional shock absorbing mechanism comgmonly employedin landing vgear of the type shown and which it is not deemed necessary to show in detail because its construction is not Otheroblects and advantages of the invention will be apparent from the following description of a preferred embodiment thereof as illustrated Referring to the drawing, Fig. 1 illustrates apertinent to .the. instant invention except that the rod and thecylinder areconnected for'rela-' tive endwise sliding movement but must rotate together.

--'I'he entire wheel structure described above 1 associated therewith a power-operated mechanism for eiiecting the steering movement of the wheel, and preferably such mechanism is of the hydraulic type and may include a cylinder and piston structure suitably mounted upon'the air plane structure and ha g a novel form of connecting means with the wheel structure. For

7 this purpose the cylinder I4 is provided with-an schematic perspective view showing in full lines the ground-enga ing position of the-front wheel of a tricycle landing gear which is mounted for movement between the ground-engaging position shownjand a retracted position illustrated in dotted lines. Preferably control mechanism is provided for the wheel whereby it can be freed fOl. limited swivelling'mov ement'or it can be positively steered in: either direction. as controlled by the pilot in the cockpit. The con- 'structionis such that the wheel is automatically v 1 adjusted to its straight-ahead position whenever the cylinder.

apertured boss 22 (Figs. 1 to 3) to receive a pin 23 having its ends engaged with respective bearing portions 24 of a link 26.. The axis of the pin 23 is perpendicular to the axis of the rod I 3 a ut which the wheel I0 is turned for steerin or swivelling' movement.

Asshown on Fig. 3 the outer end of link 26 may be formed as a ball 21 which is received in a split socket 28 at the end of piston rod 29. Within the cylinder 3|, piston rod*29 carries pisten 32 which in the straight-ahead position of.

the wheel I0 is disposed midway of the ends of The cylinder 3| (Fig. 1) is mounted for limited pivotal movement in a horizontal plane by respective trunnions' 33 thereon engaging bearings 34 of the airplane structure. In, I this waythe piston and cylinder structure can pivot slightly during endwise movement of thepiston rod to accommodate the arcuate movement of the link 26 about the axis of the rod 13.

Hydraulic means is provided for controlling of the piston 32 respective lines 36 and 31 which are preferably of flexible construction, are connectedto the respective ends of the cy der and lead to opposite sides of a steering co trol valve 33 of a.conventional design and having a pressure line 39 and a return line 40 connected thereto. The line 39 leads. from a suitableisource of hydraulic pressure while line 40 empties into the source of liquid supply therefor. v 3

To provide for control of the valve, rotoffl thereof carries a sprocket gear 43 which is connected by a chain 44. with a sprocket gear 46 :on a hollow shaft 31 which is -iournalled in suitable brackets 48 in the cockpit of the airplane. ,At its rearward end, the shaft 41 is provided with forked end 49 in which. handle 5| is pivoted'at 52 for movement between an operative full line position shown in Fig. 1 and an inoperative position as shown in dotted lines.

With the handle 5| in its full line-position as shown, it can be rocked in either direction as indicated by the arrows to connect the pressure line 39 to either side of the piston 32 sothat the wheel l0 can be moved in either direction to eifect steering of the airplane.

By-pass valve means are provided for disablin the steering mechanism when the handle is moved from the full line position shown to the inoperative dotted line position and this means preferably includesa by-pass line 56 connected between the lines- 36 and 31 and having a valve casing 51 (Figs. 1 and 4) incorporated therein with an apertured spring-urged plunger 53 disposed in the casing. In the position shown in Fig, 4 the plunger 58 closes the two sides of line 58 so that the by-pass is disabled. However, if

.cylinder II and towed, line position ,when the by-pass valve will be opened and the piston rod move in response to swivelling of the wheel.

One feature of my invention lies in the automatic adjustment of the wheel ll toits straiehtahead position when it is retracted, irrespective of whether or not it is in such position whilein its ground-engaging position. Also the wheel can be retracted, whether or not the handle 5! is in its inoperative position, and the wheel II will turn to its straight ahead position. Asthe strut structure I! is revolved in its bearings ID, the link 26 will turn about its pivot 23 and at the same time will effect turning movement of the the rod l3 so that when the wheel reaches its retracted position it will be turned to its straight-ahead position when the pivotal axis 23 is substantialiy upright as shown in Fig. 3. If the piston 32 is locked in position, the pivoting movement of link 23 provides for the movement of the wheel to its straight-ahead position without aflecting the position of the piston.

I claim:

1. In an airplane, airplane structure, strut means pivotally supported on said structure, a wheel, pivotal connecting means between said wheel and said strut means to provide for steerthe plunger is moved rearwardly to align hole 59 with the line 56, the by-pass will be opened and the piston 32 can be moved in either direction in its cylinder in response to swivelling movement of the wheel [0. To control the position of the plunger 58, a rod 6| which may be formed integrally with the plunger extends outwardly through screw plug 62 and is slidably disposed within the hollow shaft I'he rearward end of rod. Si is operatively engaged with the hub 63 of control handle 5|. Hub 63 is provided with cam 64 (Fig. 4) which in. the horizontal position of the control handle becomes effective to move rod SI and plunger 58 rearwardly to align hole 59 with thetwo sides of line 56. In

this manner the steering mechanism can be dis-' abled. Y J

I The operation of the landing 'gear'and the steering mechanism therefor is as follows: With the wheel Iii in the position shown, the pilot of' the airplane moves the control handle 5| either to the right or the left in accordance with the direction inwhich he wishes to turn the wheel Ill, so that either one of the lines 38 or 31 are connected with-the pressure line 38. The liquid pressure forces the piston toward the front or the rear of thecylinder 3| tow correspondingly effect turning of the wheel I (I. When the desired amount of turning is accomplished, the handle 5! is restored its upright neutral position,

and the wheel I0 is thereby locked hydraulically in its adjusted position.

If it is desired to disable the steering mechanism as for example when the airplane is being log and swivelling movement of said wheel, said connecting means including a shock-absorbing connection, said strut means and said wheel beinfi movable to place said wheel in a retracted position or in a lowered ground-engag position, a source of fluid pressure, and steerin means for said wheel including a pressure cylinder and valve control means between said cylinder and said source of pressure, said cylinder having a pivotal connection with said wheel lying in a plane containing the axis of said cylinder f in the lowered position of said wheel and lying in a plane substantially at a right angle to said cylinder axis in the retracted position .of said wheel.

2. In an airplane, airplane structure, a wheel, means connecting said wheel-to said structure for movement-between a ground-engaging position and a retracted position including means providing for steering movement of said wheel, hydraulic means for effecting said steering movement, said hydraulic means including a bypass vaive for conditioning said wheel for free swivelling movement, and control means having one position for opening said by-pass valve and another position for closing said by-pass valve and for causing steering movement of said wheel in either direction. V

3; In an airplane, airplane structure, a wheel structure, means connecting said wheel structure movement of said wheel structure, hydraulic means for effecting said steering movement including a piston and cylinder structure and control means therefor, and a linkage having a piv otal connection with said wheel structure about an axis perpendicular to the axis of said steering movement and having a universal connection with said piston and cylinder structure.

4. In an airplane, airplane structure, a wheel structure, a pivotal connection between said wheel structure and said airplane structure providing for swinging "movement of said wheel structure between a ground-engaging position the handle 3| can be moved joits'dotted a will be free to 2,279,074 and a retracted position, means for effecting steering movement of said wheel structure, said last-named means including a linkage having a pivotal connection with said wheel structure about an axis perpendicular to the axis of said steering movement, and an operating rod having I v a universal connection with said linkage, whereby said wheel structure will be adjusted to straight ahead position when retracted irrespective of steering adjustment thereof in said ground engaging position.

5. In an airplane, airplane structure, a wheel, means connecting said wheel-to said structure movement of said wheel in either direction.

- C. STEARMAN. 

